// Copyright (c) 2009-2019 The Regents of the University of Michigan
// This file is part of the HOOMD-blue project, released under the BSD 3-Clause License.

// Maintainer: Lin Yang, Alex Travesset
// Previous Maintainer: Morozov

#include "hoomd/ForceCompute.h"
#include "hoomd/md/NeighborList.h"

#include <memory>

/*! \file EAMForceCompute.h
 \brief Declares the EAMForceCompute class
 */

#ifdef NVCC
#error This header cannot be compiled by nvcc
#endif

#include <hoomd/extern/pybind/include/pybind11/pybind11.h>

#ifndef __EAMFORCECOMPUTE_H__
#define __EAMFORCECOMPUTE_H__

//! Computes the potential and force on each particle based on values given in a EAM potential
/*! \b Overview
 The total potential and force is computed for each particle when compute() is called. Potentials and
 forces are only computed between neighbouring particles with a separation distance less than
 \c r_cut. A NeighborList must be provided to identify these neighbours.

 \b Interpolation
 The cubic interpolation is used. For each data point, including the value of the point, there are 3
 coefficients.

 \b Potential memory layout
 The potential data and the coefficients are stored in six GPUArray<Scalar> arrays: the embedded
 potential function (m_F) and its derivative (m_dF), the electron density function (m_rho) and its
 derivative (m_drho), the pair potential function (m_rphi) and its derivative (m_drphi). The 3
 coefficients for a data point is stored continuously, for example, h_F.data[100].w is the embedded
 potential function's value read from the 100st position of the potential file,
 h_F.data[100].z, h_F.data[100].y, h_F.data[100*].x, are for interpolating embedded function,
 h_dF.data[100].z, h_dF.data[100].y, h_dF.data[100].x, are for interpolating derivative embedded
 function.

 \ingroup computes
 */
class EAMForceCompute: public ForceCompute
    {
public:
    //! Constructs the compute
    EAMForceCompute(std::shared_ptr<SystemDefinition> sysdef, char *filename, int type_of_file);

    //! Destructor
    virtual ~EAMForceCompute();

    //! Sets the neighbor list to be used for the EAM force
    virtual void set_neighbor_list(std::shared_ptr<NeighborList> nlist);

    //! Get the r cut value read from the EAM potential file
    virtual Scalar get_r_cut();

    //! Returns a list of log quantities this compute calculates
    virtual std::vector<std::string> getProvidedLogQuantities();

    //! Calculates the requested log value and returns it
    virtual Scalar getLogValue(const std::string &quantity, unsigned int timestep);

    //! Load EAM potential file
    virtual void loadFile(char *filename, int type_of_file);

protected:
    std::shared_ptr<NeighborList> m_nlist; //!< the neighborlist to use for the computation
    Scalar m_r_cut;                        //!< cut-off radius
    unsigned int m_ntypes;                 //!< number of potential element types
    unsigned int nrho;                     //!< number of tabulated values of interpolated F(rho)
    Scalar drho;                           //!< interval of rho in interpolated table
    Scalar rdrho;                          //!< 1.0 / drho
    unsigned int nr;                       //!< number of tabulated values of interpolated rho(r), r*phi(r)
    Scalar dr;                             //!< interval of r in interpolated table
    Scalar rdr;                            //!< 1.0 / dr
    std::vector<double> mass;              //!< array mass(type)
    std::vector<int> types;                //!< array type(id)
    std::vector<int> nproton;              //!< atomic number
    std::vector<double> lconst;            //!< lattice constant
    std::vector<std::string> atomcomment;  //!< atom comment
    std::vector<std::string> names;        //!< array names(type)

    GPUArray<Scalar4> m_F;                 //!< embedded function and its coefficients
    GPUArray<Scalar4> m_rho;               //!< electron density and its coefficients
    GPUArray<Scalar4> m_rphi;              //!< pair wise function and its coefficients
    GPUArray<Scalar4> m_dF;                //!< derivative embedded function and its coefficients
    GPUArray<Scalar4> m_drho;              //!< derivative electron density and its coefficients
    GPUArray<Scalar4> m_drphi;             //!< derivative pair wise function and its coefficients
    GPUArray<Scalar> m_dFdP;               //!< derivative F / derivative P

    //! Actually compute the forces
    virtual void computeForces(unsigned int timestep);

    //! Method to be called when number of types changes
    virtual void slotNumTypesChange()
        {
        m_exec_conf->msg->error() << "Changing the number of types is unsupported for pair.eam" << std::endl;
        throw std::runtime_error("Unsupported feature");
        }

    //! cubic interpolation
    virtual void interpolation(int num_all, int num_per, Scalar delta, ArrayHandle<Scalar4> *f,
            ArrayHandle<Scalar4> *df);
    };

//! Exports the EAMForceCompute class to python
void export_EAMForceCompute(pybind11::module &m);

#endif
